Pillared-layer Ni-MOF nanosheets anchored on Ti3C2 MXene for enhanced electrochemical energy storage

Abstract

The poor conductivity, unsatisfactory stability and easy aggregation of metal–organic framework (MOF) nanomaterials have been recognized as the main reasons that prevent their practical application. Here, we report the highly conductive and cyclic-stable Ti3C2 MXene@pillared-layer [Ni(thiophene-2,5-dicarboxylate)(4,4′-bipyridine)]n MOF composites (MXene@Ni-MOF). Based on the hard-soft-acid-base principle, the pillared-layer Ni-MOF porous structure with Ni-N coordination bonds confer better structural stability. The Ni-MOF nanosheets are immobilized by the MXene, leading to fast charge transfer between the Ni-MOF and MXene, solving the problem of poor conductivity of Ni-MOF, while avoiding the agglomeration of Ni-MOF nanosheets. Moreover, the strong interaction between the organic ligands of Ni-MOF and surface functional groups of MXene plays a key role: it reduces the exposure of surface groups of MXene, limits the oxidation of MXene, and increases its layer spacing, thus facilitating the rapid ion transport. The MXene@Ni-MOF exhibits a high specific capacitance (979 F g−1 at 0.5 A g−1) and the new aqueous asymmetric supercapacitor device displays an excellent cycling property with only 2% decay after 5000 cycles.